mike davis

THE COMING DESERT

Kropotkin, Mars and the Pulse of Asia

Anthropogenic climate change is usually portrayed as a recent discovery, with a genealogy that extends no further backwards than Charles Keeling sampling atmospheric gases from his station near the summit of Mauna Loa in the 1960s, or, at the very most, Svante Arrhenius’s legendary 1896 paper on carbon emissions and the planetary greenhouse. In fact, the deleterious climatic consequences of economic growth, especially the influence of deforestation and plantation agriculture on atmospheric moisture levels, were widely noted, and often exaggerated, from the Enlightenment until the late nineteenth century. The irony of Victorian science, however, was that while human influence on climate, whether as a result of land clearance or industrial pollution, was widely acknowledged, and sometimes envisioned as an approaching doomsday for the big cities (see John Ruskin’s hallucinatory rant, ‘The Storm Cloud of the Nineteenth Century’), few if any major thinkers discerned a pattern of natural climate variability in ancient or modern history. The Lyellian world-view, canonized by Darwin in The Origin of Species, supplanted biblical catastrophism with a vision of slow geological and environmental evolution through deep time. Despite the discovery of the Ice Age(s) by the Swiss geologist Louis Agassiz in the late 1830s, the contemporary scientific bias was against environmental perturbations, whether periodic or progressive, on historical time-scales. Climate change, like evolution, was measured in eons, not centuries.

He maintains that as a result of cultivation and in proportion to its degree, the ‘damp’ so much beloved by the peasant is lost (hence too plants emigrate from south to north) and eventually the formation of steppes begins. The first effects of cultivation are useful, later devastating owing to deforestation, etc. This man is both a thoroughly learned philologist (he has written books in Greek) and a chemist, agricultural expert, etc. The whole conclusion is that cultivation when it progresses in a primitive way and is not consciously controlled (as a bourgeois of course he does not arrive at this), leaves deserts behind it, Persia, Mesopotamia, etc., Greece. Here again another unconscious socialist tendency!
[16]
Marx to Engels, 25 March 1868, in Collected Works, vol. 42, Moscow 1987, pp. 558–9.

There is devilishly little left of ‘nature’ as it was in Germany at the time when the Germanic peoples immigrated into it. The earth’s surface, climate, vegetation, fauna, and the human beings themselves have infinitely changed, and all this owing to human activity, while the changes of nature in Germany which have occurred in this period of time without human interference are incalculably small.
[18]
Collected Works, vol. 25, Moscow 1987, p. 511.

Desiccation of Asia and Mars

Kropotkin radically challenged this orthodoxy by asserting a continuity of global climatic dynamics between the end of the Ice Age and modern times; far from being stationary as early meteorologists believed, climate had been continuously changing in a unidirectional sense and without human help throughout history. In 1904, on the thirtieth anniversary of his original presentation to Russian geographers, and amidst much public interest in recent expeditions to inner Asia by the Swedish geographer Sven Hedin and the American geologist Raphael Pumpelly, the Royal Geographical Society invited Kropotkin to outline his current views.

Kropotkin’s hypothesis of natural, progressive climate change had a differential reception: greeted with more scepticism in continental Europe than in English-speaking countries or amongst scientists working in desert environments. In Russia, where his contributions to physical geography were well known, there had been intense interest, following the great famine of 1891–92, in understanding whether drought on the black-soil steppe, the new frontier of wheat production, was a result of cultivation or an omen of creeping desertification. In the event, the two internationally recognized authorities on the question, Aleksandr Voeikov—a pioneer of modern climatology, and an old colleague of Kropotkin’s from the Geographical Society in the early 1870s—and Vasili Dokuchaev—celebrated as ‘the father of soil science’—found little evidence of either process at work. In their view, the steppe climate had not changed in historical time, although the succession of wet and dry years might be cyclical in nature. Voeikov, like many other contemporary scientists in Europe, was intrigued if not convinced by the ideas about climate variability advanced by the brilliant German glaciologist Eduard Brückner.
[27]
David Moon, The Plough that Broke the Steppes: Agriculture and Environment on Russia’s Grasslands, 1700–1914, Oxford 2013, pp. 91–2, 130–3.

Newspaper readers across the globe were electrified, composers wrote Mars marches, and an English journalist named Wells found the plot for a book that continues to fascinate and terrify readers. Lowell quickly acquired implacable scientific foes, such as the co-discoverer of natural selection and acquaintance of Kropotkin, Alfred Russel Wallace; but with the popular press as an ally, he soon convinced public opinion that a Martian civilization was fact, not speculation. He liked to astound audiences with photographs of the ‘canals’, always apologizing for the blurred images.
[32]
Alfred Russel Wallace, Is Mars Habitable?, London 1907. But what was the nature and history of this alien civilization? Lowell may have met Kropotkin when the latter gave a series of lectures on evolution at Boston’s Lowell Institute in 1901, but whatever the case may be, the 1904 paper on progressive desiccation struck Lowell like a lightning bolt. Here was a master narrative to explain not only the ‘tragedy of Mars’ but also the fate of the Earth. Lowell argued that because of its smaller size, planetary evolution was accelerated on Mars, thus providing a preview of how the Earth would change in eons to come. ‘On our own world’, he wrote in the 1906 book Mars and Its Canals, ‘we are able only to study our present and our past; in Mars we are able to glimpse, in some sort, our future.’ That future was planetary desiccation as oceans evaporated and dried into land, forest gave way to steppe, and grasslands became deserts. He agreed with Kropotkin about the velocity of aridification: ‘Palestine has desiccated within historic times.’
[33]
Percival Lowell, Mars and its Canals, New York 1906, pp. 153, 384. I have been unable to ascertain Kropotkin’s opinion of Lowell’s thesis. By scientific temperament he was more likely to have agreed with his friend Wallace.

Two years later, in popular talks published under the title Mars as Abode of Life, he devoted a lecture to ‘Mars and the Future of Earth’, warning that ‘the cosmic circumstance about them which is most terrible is not that deserts are, but that deserts have begun to be. Not as local, evitable evils only are they to be pictured, but as the general unspeakable death-grip on our world.’ His prime example, not surprisingly, was Central Asia: ‘The Caspian is disappearing before our eyes, as the remains, some distance from its edge, of what once were ports mutely inform us.’ Someday, the only option left to humans in this ‘struggle for existence in their planet’s decrepitude and decay’ would be to emulate the Martians and build canals to bring polar water to their last oases.
[34]
Lowell, Mars as Abode of Life, New York 1908, pp. 122, 124, 142–3. Lowell, a skilled mathematician but a hapless geologist, liked to impress visitors to Arizona with the Petrified Forest as an example of desiccation at work, although the tree fossils dated from the Triassic Period, 225 million years earlier. Likewise he took for granted the evidence for unidirectional and rapid climate change on Earth.

In fact, Kropotkin’s theory, based on landscape impressions and the hypothesis of a Eurasian ice sheet, was a speculative leap far ahead of any data about past climates or their causes. Indeed it was essentially untestable. Theoretical as contrasted to descriptive meteorology, for example, was still in its swaddling clothes. By coincidence, Kropotkin’s paper was published almost simultaneously with an obscure article by a Norwegian scientist named Jacob Bjerknes that laid down the first foundations for a physics of the atmosphere, in the form of a half dozen fundamental equations derived from fluid mechanics and thermodynamics. ‘He [Bjerknes] conceived the atmosphere’, observes a historian of geophysics, ‘from a purely mechanical and physical viewpoint, as an “air-mass circulation engine”, driven by solar radiation and deflected by rotation, expressed in local differences of velocity, density, air pressure, temperature and humidity.’ It would take more than half a century for these conceptual seeds to grow into modern dynamic meteorology; in the meantime, it was impossible to propose a climate model for Kropotkin’s theory.
[35]
Gabriele Gramelsberger, ‘Conceiving Processes in Atmospheric Models’, Studies in the History and Philosophy of Modern Physics, vol. 41, no. 3, September 2010.

Quantitative evidence for understanding past climate was likewise a bare cupboard. Brückner had used instrumental records with impressive skill, but only for the period after the French Revolution. In 1901, the Swedish meteorologist Nils Ekholm, writing in the Quarterly Journal of the Royal Meteorological Society, had soberly surveyed the available pre-instrumental documentary evidence and found that much of it was simply worthless: ‘Almost the only weather phenomenon of which the old chronicles give trustworthy reports are severe winters.’ Comparing Tycho Brahe’s pioneering instrumental weather readings in 1579–82 from an island off the Danish coast with modern measurements from the same location, he found some indications that winters were milder and that Northern European climate in general was more ‘maritime’ than three centuries earlier. But this was the limit of disciplined inference: ‘The character in other respects and the cause of this variation are unknown. We cannot say if the variation is periodical, progressive or accidental, nor how far it extends in space and time.’ Since Ekholm reasonably assumed that insolation had been constant for at least a million years and that the Earth’s orbital variability had had minimal influence over the last millennium of climate, the most likely cause of climate change (based on the famous experiments of his colleague Svante Arrhenius) was a fluctuation in atmospheric carbon dioxide and thereby the greenhouse effect.
[36]
Nils Ekholm, ‘On the Origins of the Climate of the Geological and Historical Past and Their Causes’, Quarterly Journal of the Royal Meteorological Society, vol. xxvii, no. 117, January 1901.

The most fervent adherent to the desiccation hypothesis, however, was the Yale geographer Ellsworth Huntington, a former missionary in Turkey and a veteran of the 1903 Pumpelly Expedition to Transcaspia and the 1905 Barrett Expedition to Chinese Turkestan. His observations from the latter mission confirmed those of earlier travellers in Xinjiang and supported Kropotkin’s theory: ‘All the more arid part of Asia, from the Caspian Sea eastward for over 2,500 miles, appears to have been subject to a climatic change whereby it has been growing less and less habitable for the last two or three thousand years.’
[40]
Ellsworth Huntington, ‘The Rivers of Chinese Turkestan and the Desiccation of Asia’, The Geographical Journal, vol. 28, no. 4, October 1906. At first Huntington vigorously defended Kropotkin’s ideas to the letter, but in his 1907 book, The Pulse of Asia, he amended the theory in one decisive regard. Considering the menu of possible climate hypotheses—‘uniformity, deforestation [anthropogenic change], progressive change, and pulsatory change’—he now voted for the last. Climate change, Huntington argued, took the form of great, Sun-driven oscillations of centuries-long duration: wet periods followed by mega-droughts.
[41]
Geoffrey Martin, Ellsworth Huntington: His Life and Thought, Hamden, ct 1973, pp. 92–3. Although he attributed the idea to reading Brückner, his cycles were an order of magnitude longer in frequency and had the epic effects ascribed to progressive desiccation by Kropotkin.

Eduard Brückner in Vienna, whom Huntington acknowledged as one of his masters, was also polite but devastating in his assessment:

He takes his data from historical works without examining it properly. He is not sufficiently aware to what degree he may use data as facts. In particular the archaeological results are by no means definitive enough as he himself explains in his work The Pulse of Asia . . . He has shown several times the desire to fit the facts to his theory. During my visit to Yale Dr Huntington showed me the results of his investigations in respect to the rings of old trees in their relationship to fluctuations of climate. He has collected very interesting material, but again I had the impression that he concluded more from his curves than a cautious man ought to conclude. He claimed in several cases that he saw a parallelism in the curve where I could not see one.
[48]
Martin, Ellsworth Huntington, p. 86.

As for spectacular ruins in the deserts, the geographer and historian Rhoads Murphey demonstrated in a 1951 article, contra Huntington, that in the case of North Africa there is little evidence of climate change since the Roman period. Instead, he explained the desolate landscapes where wheat fields and Roman towns once flourished as a result of the neglect or destruction of water-storage infrastructures. (Huntington seemed to have forgotten the dependence of desert societies upon groundwater rather than rain.) In a classic example of the kind of ‘natural experiment’ that Jared Diamond would decades later urge historians to adopt, Murphey cited the example of the Aïr Massif in Niger where the French forcibly evicted the rebellious Tuareg population in 1917: ‘As population decreased, wells, gardens and stock were allowed to deteriorate, and within less than a year the area looked exactly like the other areas which have been used as evidence of progressive desiccation.’
[52]
Rhoads Murphey, ‘The Decline of North Africa since the Roman Occupation: Climatic or Human?’, Annals of the Association of American Geographers, vol. 41, no. 2, 1951.

For all this, the Kropotkin/Huntington debate about natural climate change in history might have left a more fruitful legacy if it had stayed within the domain of physical geography. Huntington, however, fused his distinctive ideas about climate cycles with the extreme environmental determinism advocated by the German geographer Friedrich Ratzel and his American disciple Ellen Churchill Semple. They argued that cultural and ethnic characteristics were mechanically and irreversibly imprinted upon human groups by their natural habitats, especially climate. Huntington also became mesmerized by the bizarre ideas of a professor of German in Syracuse named Charles Kullmer who believed that human mental activity, both individual and social, was governed by the electrical potential of barometric depressions. As Huntington’s biographer explains: ‘Kullmer measured the number of nonfiction books taken from libraries and the barometric pressure at such time; “high pressure means more serious books, and low pressure fewer.”’ Huntington, ‘electrified’ by Kullmer’s findings, wrote ‘I have pondered a great deal over the Italian Renaissance; and now I am wondering whether by any chance that was associated with some change in storm frequency.’ Huntington subsequently tested Kullmer’s thesis by having a friend’s children type three dictated stanzas of Spencer’s The Faerie Queene every day for months while their father recorded the barometric pressure. Huntington then compared the pattern of errors: ‘There seems to be a connection between weather and mental ability far closer than we have hitherto suspected. I am at work just now trying to apply this to Japan.’
[53]
Martin, Ellsworth Huntington, pp. 102–3, 111.

In the 1910s and 1920s, the heyday of scientific racism (of which Huntington was a fervent proponent), these ideas were easily embraced by mainstream scholarship; by the late 1930s, however, a new generation of academics began to recoil from the dark implications of environmental determinism alloyed with white supremacy and its apotheosis, fascism. As his biographer gingerly observes: ‘Huntington’s insistence on a hierarchy of innate competence, and consistent inquiry into the eugenic cause in the 1930s, was perhaps unfortunate. When he proposed on the eve of World War ii that Caucasians with blond hair and blue eyes were possessed of greater longevity than others, his utterance seemed peculiarly non sequitur.’
[57]
Martin, Ellsworth Huntington, pp. 249–50. (The Nazis, meanwhile, were integrating desiccationist ideas into their rationale for the removal and mass murder of the populations of Poland and the ussr. The Slavs were simultaneously condemned for failing to drain the post-glacial wetlands east of the Vistula and for allowing them to turn into desert—Versteppung. Only the master race could arrest the great drying.
[58]
David Blackbourn, The Conquest of Nature: Water, Landscape, and the Making of Modern Germany, New York 2006, pp. 278, 285–6. ) Huntington’s wild theories and crude determinism, together with the absence of reliable historical weather data, began to taint the enterprise of climate history for most geographers and historians. In 1937, the physicist Sir Gilbert Walker, who had spent a lifetime searching for structure in weather data, wrote an obituary for climatic determinism, a theory he equated with astrology: ‘I regard the widespread faith in the effective control of weather by periods as based partly on a mistaken handling of plotted data and partly on an instinct that survives in many of us, like the faith in the effect of the Moon on the weather, from the time when our forefathers believed in the control of human affairs by the heavenly bodies with their fixed cycles.’
[59]
Sir Gilbert Walker, ‘Climatic Cycles: Discussion’, The Geographical Journal, vol. 89, no. 3, March 1937.

In the postwar period, moreover, ‘a new disciplinary consensus’ emerged amongst climatologists: ‘Namely that the global climate system contained overriding equilibrating processes providing resilience against secular climate fluctuations.’
[60]
Stehr and von Storch, ‘Eduard Brückner’s Ideas’, p. 12. Meanwhile, the natural archives of deep Eurasia that hid the secrets of its climate history were off-limits: the only Westerners to visit the Tarim Basin during the Cold War were cia agents (Lop Nor was the Chinese nuclear test site). Finally in 2010–11, more than a century after the controversial expeditions of Stein, Heden and Huntington, an interdisciplinary team of Chinese, American, Swiss and Australian researchers spent a field season in the Tarim Basin, modelling relict hydrologies and sampling such potential climate archives as sediments from the now vanished Lake Lop Nor and dead trees interred in sand dunes.

Their results were published at the beginning of this year. Desiccation, it turns out, is a modern phenomenon, not an ancient curse: ‘The Tarim Basin was continuously wetter than today at least as early as ad 1180 until the middle ad 1800s.’ This falls within the parameters, generously construed, of the Little Ice Age, and the researchers attribute the wetting to a southward shift of the boreal westerlies that produced enhanced snowfall in the mountains that feed the Tarim and its sister rivers. It was this ‘greening of the desert’, not its relentless expansion, that was a mainspring of late medieval and early modern history:

[1] ‘It was assumed that for all practical purposes and decisions, climate could be considered constant.’ Hubert Lamb, Climate, History and the Modern World, London 1995, p. 2. This essay will appear in a forthcoming book, edited by Cal Winslow, A Search for the Commons: Essays for Iain Boal, to be published by pm Press.

[2] George Woodcock and Ivan Avakumovic, The Anarchist Prince: The Biography of Prince Peter Kropotkin, London 1950, p. 71.

[4] Woodcock and Avakumovic, The Anarchist Prince, pp. 61–86. On his recognition of the plateau as a fundamental landform, see Alexander Vucinich, Science in Russian Culture: 1861–1917, Palo Alto 1970, p. 88.

[5] Woodcock and Avakumovic, The Anarchist Prince, p. 73. In later years, there would be fierce debate over historical fluctuations in the level and areal expanse of the Caspian, but the controversy, like so many others, was unresolvable in the absence of any technique for dating land features. From mid-century, however, the hypothesis of creeping desertification in Central Asia was familiar to the educated public: for an example, see Frederick Engels, The Dialectics of Nature [1883], New York 1940, p. 235.

[7] ‘The desiccation I speak of is not due to a diminishing rainfall. It is due to the thawing and disappearance of that immense stock of frozen water which had accumulated on the surface of our Eurasian continent during the tens of thousands of years that the glacial period had been lasting. Diminishing rainfall (where such a diminution took place) is thus a consequence, not a cause of that desiccation.’ Kropotkin, ‘On the Desiccation of Eurasia and Some General Aspects of Desiccation’, The Geographical Journal, vol. 43, no. 4, April 1914.

[8] His brother Alexander oversaw the publication of the first volume, 828 pages in length: Issledovanie o lednikovom periode [Researches on the Glacial Period], St Petersburg 1876. A short review appeared in Nature on 23 June 1877. An incomplete draft of the second volume was seized by the secret police and not published until 1998: Tatiana Ivanova and Vyacheslav Markin, ‘Piotr Alekseevich Kropotkin and his monograph Researches on the Glacial Period (1876)’, in Rodney Grapes, David Oldroyd and Algimantas Grigelis, eds, History of Geomorphology and Quaternary Geology, London 2008, p. 18.

[9] The famed California geologist Josiah Whitney (after whom the peak is named) had also been advocating a concept of progressive desiccation since at least the early 1870s. He dismissed the popular idea that deforestation was responsible for climate change, instead proposing that the Earth had been simultaneously drying and cooling for several million years. This theory put him in the odd position of arguing that the modern climate of the American West was colder than during the Ice Age; a contradiction he resolved by rejecting evidence for the existence of continental ice sheets. In his view, Agassiz and others had confused the strictly local phenomena of glacial advance with global refrigeration. See Whitney, The Climatic Changes of Later Geological Times: A Discussion Based on Observations Made in the Cordilleras of North America, Cambridge, ma 1882, p. 394.

[11] Already by the mid-eighteenth century, colonial officials were crusading for the establishment of forest reserves to prevent desiccation of the rich plantation islands of Tobago and Mauritius. Richard Grove, the historian who has done most to establish the colonial origins of environmentalism, cites the example of Pierre Poivre, commissaire-intendant of Mauritius. Poivre gave a major speech in Lyon in 1763 on the climatic dangers of deforestation. ‘This speech may go down in history as one of the first environmentalist texts to be based explicitly on a fear of widespread climate change’: Grove, ‘The Evolution of the Colonial Discourse on Deforestation and Climate Change, 1500–1940’, in Ecology, Climate and Empire, Cambridge 1997, p. 11. Seventy years later, July Monarchy propagandists invoked the desertification of North Africa by the Arabs as an excuse for conquest of Algeria. The French promised to change the climate and push back the desert by massive afforestation: Diana Davis, Resurrecting the Granary of Rome: Environmental History and French Colonial Expansion in North Africa, Athens, oh 2007, pp. 4–5, 77.

[12] Buffon believed that land clearance changed temperature as well as rainfall. Since Paris and Quebec City were at the same latitude, he suggested that the most likely explanation for their different climates was the warming that resulted from draining the wetlands and cutting down the forests around Paris: Clarence Glacken, Traces on the Rhodian Shore, Berkeley 1976, p. 699.

[15] Karl Fraas, Klima und Pflanzenwelt in der Zeit: ein Beitrag zur Geschichte Beider [Climate and Plant World Over Time: A Contribution to History], Landshut 1847. Fraas was an important influence on Perkins Marsh and his famous thesis in Man and Nature that humanity was catastrophically reshaping nature on a global scale.

[17] Engels, ‘The Part Played by Labour in the Transition from Ape to Man’, in The Dialectics of Nature, pp. 291–2. Even in the case of contemporary industrial civilization, he wrote, ‘we find that there still exists here a colossal disproportion between the proposed aims and the results arrived at, that unforeseen effects predominate, and that the uncontrolled forces are far more powerful than those set into motion according to plan’: p. 19.

[19] Both Newton and Halley believed in ‘a succession of earths, a series of creations and purgations. Historical periods were punctuated by cometary catastropes, with comets serving as divine agents to reconstitute the entire solar system, to prepare sites for new creations and to usher in the millennium’: Sara Genuth, ‘The Teleological Role of Comets’, in Norman Thrower, ed., Standing on the Shoulders of Giants: A Longer View of Newton and Halley, Berkeley 1990, p. 302.

[20] Anne O’Connor, Finding Time for the Old Stone Age: A History of Palaeolithic Archaeology and Quaternary Geology in Britain, 1860–1960, Oxford 2007, pp. 28–30.

[21] Kruger, Discovering the Ice Ages, p. 475. In the early twentieth century, varve (annual lake-sediment layer) and tree-ring chronologies began to be used to calculate the age of deglaciation events, but it was not until the refinement of carbon-14 analysis in the postwar period that reliable dating became possible.

[26] Kropotkin, ‘The Desiccation of Eur-Asia’. Desiccation, of course, is a geomorphological fact in many landscapes, but the impressionistic archaeology of European explorers neither proved causal relationships between ruins and desertification, nor established a comparative chronology. Petra, for instance, is an oft-cited example of catastrophic climate change, but the city-state’s decline was actually the result of changing trade routes and a 333 ad earthquake that destroyed its elaborate water-supply system.

[31] ‘To talk of Martian beings is not to mean Martian men. Just as the probabilities point to the one, so do they point away from the other. Even on this Earth man is of the nature of an accident. He is the survival of by no means the highest physical organism. He is not even a high form of mammal. Mind has been his making. For aught we can see, some lizard or batrachian might just as well have popped into his place early in the race, and been now the dominant creature of this Earth. Under different physical conditions, he would have been certain to do so. Amid the surroundings that exist on Mars, surroundings so different from our own, we may be practically sure other organisms have been evolved of which we have no cognizance.’ Percival Lowell, Mars, Boston 1895, p. 211.

[33] Percival Lowell, Mars and its Canals, New York 1906, pp. 153, 384. I have been unable to ascertain Kropotkin’s opinion of Lowell’s thesis. By scientific temperament he was more likely to have agreed with his friend Wallace.

[35] Gabriele Gramelsberger, ‘Conceiving Processes in Atmospheric Models’, Studies in the History and Philosophy of Modern Physics, vol. 41, no. 3, September 2010.

[36] Nils Ekholm, ‘On the Origins of the Climate of the Geological and Historical Past and Their Causes’, Quarterly Journal of the Royal Meteorological Society, vol. xxvii, no. 117, January 1901.

[37] Curzon’s comments described in Sidney Burrard, ‘Correspondence’, The Geographical Journal, vol. 43, no. 6, June 1914. Curzon was speaking in defence of his friend Sir Thomas Holdich of the Royal Engineers, who became a convinced desiccationist after a lifetime surveying the Northwest Frontier of India.

[38] When the workers on the family estates occupied the land during the Biennio Rosso, Caetani abdicated his titles to his younger brother and emigrated to Vernon, a town at the foot of the magnificent Selkirk mountains in British Columbia where in his younger days he had once hunted grizzly bears. After his death in 1935, his wife and daughter, an accomplished artist, became legendary recluses: see Sveva Caetani, Recapitulation: A Journey, Vernon, bc 1995; and ‘Sveva Caetani: A Fairy Tale Life’, available online.

[42] Douglas (1867–1962) had been Lowell’s principal assistant in the ‘mapping’ of the Martian canals before becoming interested in the possible relationship between sunspot activity and rainfall. He refined the use of ring-width in trees as a proxy for weather, an endeavour properly called dendroclimatology. But his techniques also opened the possibility of dating ancient trees or, for that matter, wooden beams in pueblo ruins. In the beginning, only a floating (relative) chronology was possible, but in 1929 Douglas discovered ‘hh-39’, a beam from an Arizona ruin that allowed him to tie together a continuous series of measurements from 700 ad to the present, and thus permit the first calendrical dating of a prehistoric archaeological site.

[43] Ellsworth Huntington, The Pulse of Asia, Boston 1907, p. 385. For his original endorsement of Kropotkin’s ideas, and his subsequent modification of them, see Huntington, ‘Climatic Changes’, The Geographical Journal, vol. 44, no. 2, August 1914.

[54] Fleming, Historical Perspectives on Climate Change, p. 100. He adds: ‘Although Huntington’s thought was indeed influential in its time, since then his racial bias and crude determinism have been largely rejected. Nonetheless, his categorical errors seem destined to be repeated by those who make overly dramatic claims for weather and climatic influences’: p. 95.

[55] It was published in Russian in 1998. An English-language anthology of Kropotkin’s scientific writings—on geography, glaciology, ecology and evolution—is long overdue.

[56] See ‘Appendix A: The Published Works of Ellsworth Huntington’ in Martin, Ellsworth Huntington.

[61] Aaron Putnam et al., ‘Little Ice Age Wetting of Interior Asian Deserts and the Rise of the Mongol Empire’, Quaternary Science Reviews, 131, 2016, pp. 333–4, 340–1. One of the co-authors is the Lamont-Doherty Earth Observatory’s ‘pope’, Wallace Broecker, who first proposed the theory of the meridional overturning circulation in the North Atlantic—the famed ‘conveyor belt’.

[62] Colin Kelley et al., ‘Climate Change in the Fertile Crescent and Implications of the Recent Syrian Drought’, Proceedings of the National Academy of Sciences, vol. 112, no. 11, 17 March 2015.